1. Field of the Invention
The invention relates to a side airbag device for a vehicle, which restrains a seated occupant by using a side airbag at the time of a side impact of the vehicle.
2. Description of Related Art
In a gas bag-type side collision protective device described in Japanese Patent Application Publication No. 2000-177527 A (JP 2000-177527 A), a gas bag (a side airbag) includes a chamber for thorax (an upper bag portion) that expands to a side of a thorax of an occupant, and a chamber for pelvis (a lower bag portion) that expands to a side of a pelvis of the occupant. It is possible to fill these chambers with gas by using a source of compressed gas so that the chambers in a filled state have different inner pressure from each other. For example, by reducing the inner pressure of the chamber for thorax so as to be smaller than the inner pressure of the chamber for pelvis, the thorax region, which is relatively vulnerable to an impact, is cushioned more softly than the pelvis.
Incidentally, a side airbag is compressed between a seated occupant and a side door as the side door intrudes into a vehicle interior side due to a force of a side impact. In such an event, the chamber for thorax and the chamber for pelvis are compressed into an oblong flat shape (an elliptical shape) when seen from a vehicle front-rear direction, and the dimension of each of the chambers in an upper-lower direction is increased. As a result, the high-pressure chamber for pelvis enters an abdominal region that has lower load resistance than the pelvis region, and a load on the abdominal region can increase.